Study of twins links early concussions to thinking, memory problems later

Scientists who studied male twins, from an average age of 67, found that earlier concussions were tied to lower scores on tests of thinking and memory. Photo by Mitrey/Pixabay

Your thinking and memory skills may take a hit decades after recovering from a concussion, a new study indicates.

Scientists who studied male twins, from an average age of 67, found that earlier concussions were tied to lower scores on tests of thinking and memory. These men also had a more rapid decline in their cognitive skills – skills needed for reasoning and the acquisition of knowledge.

“It is concerning and, honestly, since previous studies had not been able to capture the cognitive decline, it was not something I really was expecting to see,” said study author Marianne Chanti-Ketterl, a gerontologist at Duke University Medical Center in Durham, N.C. “But it is also promising because it’s something that we can intervene on.”

Studying identical twins makes sense because they share the same genes and many of the same early life exposures. In this research, one person from each pair had sustained a traumatic brain injury (TBI) during their lifetime and the other hadn’t been injured.

This study worked with data from nearly 7,200 white, male World War II veterans who were twins. The men took a thinking skills test when the study began, at age 67 on average. They took the tests three more times over 12 years. Those with a history of concussion had the brain injury 34 years earlier on average.

Participants started with an average score of 32.5 out of 50, the study authors noted.

The results showed that participants who had had a concussion were more likely than their uninjured twin to have lower test scores at about age 70. That was especially true if they had lost consciousness from the impact or were older than 24 at the time of the injury.

The twin with the injury had a test score that was 0.59 lower at 70 than the other twin, and thinking skills declined faster, by 0.05 points per year.

The effect sizes are modest, Chanti-Ketterl said, but may be enough to trigger an evaluation for cognitive impairment.

“A lot of people, they have mild traumatic brain injuries and they don’t seek medical help because they think it’s not going to affect them later in life. And now we know that it does,” Chanti-Ketterl said.

If the research leads to acknowledging and understanding the impact a TBI has on the rate of cognitive decline later in life, a physician may be better able to identify individuals at risk and follow them more closely, Chanti-Ketterl said.

People may also be able to help themselves with early interventions to slow cognitive decline and potentially delay the onset of dementia, she suggested.

“Knowing this information empowers you to be a little more proactive and do something to keep cognitively engaged,” Chanti-Ketterl added. Keeping socially involved, physically active and treating hearing loss are steps in the right direction.

The study was on brain injuries that occurred mostly in early adulthood, so the results don’t really suggest what happens when someone has a concussion as a child. Nor does it provide the kind of answers parents might need when weighing considerations about contact sports and safety.

It will be important for scientists to research that age group, too, Chanti-Ketterl noted.

“Unfortunately, the studies in children just end in early life. And so we are still not knowing how those early life concussions may impact their aging process,” Chanti-Ketterl said.

Dr. Holly Elser, an epidemiologist and resident physician in neurology at the University of Pennsylvania, co-wrote an editorial accompanying the research paper.

Elser thinks the historical data set the authors used is a positive aspect of the study because it allowed for an extensive period of follow-up.

“In many instances you’ll have a compelling question in front of you that cannot be answered without long duration of follow up,” Elser said.

Given what this study shows about the impact of concussion on future brain health, Elser offered suggestions for eliminating or limiting those risks.

Prevention is key, including wearing a helmet when you ride a bicycle and a seatbelt when traveling by car.

“Those are two great examples of good preventative measures,” Elser said, noting they may prevent a head injury or perhaps make one milder.

Although this study focused on head injuries sustained by younger adults, Elser noted that head injuries are prevalent in older adults, with falls a common source of these.

It’s extremely important, she said, to have and use the appropriate assistive devices to help prevent falls. These could include canes, walkers and grab bars.

The findings were published online Wednesday in Neurology. The TBIs were self-reported, which is a limitation since personal recollections aren’t always accurate.

The U.S. National Institute on Aging and the U.S. Department of Defense provided support for the research.